As argued above, BCC is linked to GS and is characterized by germline mutations of Ptch1 and SuFu. Accordingly, sporadic BCC presents hyperactivated Hh signaling, associated with inactivating mutations in Ptch1 and activating mutations in SMO, with a high-rate frequency (Gailani et al., 1996; Reifenberger et al., 1998; Xie et al., 1998). Here, PTCH1 is linked to skin basal cell carcinoma.